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Proceedings Paper

Magnetic-resonance-guided directional transurethral ultrasound thermal therapy
Author(s): Anthony Ross; Chris J. Diederich; William H. Nau; Per Daniel Tyreus; Harchi Gill; Donna Bouley; R. Kim Butts; Viola Rieke; Bruce Daniel; Graham Sommer
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Paper Abstract

Two catheter-based transurethral ultrasound applicators designed for selective thermal coagulation of prostate tissue were evaluated. The first applicator utilized two 3.5 mm piezoelectric sectored tubes with the active transducer surface forming 90°. The second applicator's transducer assembly consisted of a linear array of 3.5 x 10 mm planar transducer elements. Both applicators operated at 8 MHz and were positioned on a 4 mm diameter catheter within an integrated expandable balloon (10 mm). Manual rotation of the transducer assembly within the balloon allowed for angular control and/or sweeping of the treatment volume. Ambient temperature degassed cooling water (~120 ml/min) was circulated inside the balloon to preserve the urethral mucosa. Acoustic efficiencies of 20-54% and acoustic beam distributions were measured. The thermal treatment characteristics of the applicator were investigated in vivo (canine prostate) under MRI guidance in an interventional open magnet (0.5 T). Magnetic resonance thermal imaging (MRTI) monitored the treatments (GRE phase mapping, multiple planes, 15 sec update intervals). Post-treatment imaging (T1 w/contrast) and TTC staining of the prostate were used to verify zones of thermal damage. Single sonications lasting 8-15 min produced coagulated zones of tissue extending to the outer boundary of the prostate while preserving 2-3 mm of urethral mucosa. Multiple sonications in sequence produced larger contiguous sectors of coagulated tissue (~ 3/4 of the gland). In summary, highly directional transurethral applicators under MRI guidance were able to produce selective and controllable thermal coagulation.

Paper Details

Date Published: 10 June 2003
PDF: 8 pages
Proc. SPIE 4954, Thermal Treatment of Tissue: Energy Delivery and Assessment II, (10 June 2003); doi: 10.1117/12.476348
Show Author Affiliations
Anthony Ross, Univ. of California/San Francisco (United States)
Chris J. Diederich, Univ. of California/San Francisco (United States)
William H. Nau, Univ. of California/San Francisco (United States)
Per Daniel Tyreus, Univ. of California/San Francisco (United States)
Harchi Gill, Stanford Univ. (United States)
Donna Bouley, Stanford Univ. (United States)
R. Kim Butts, Stanford Univ. (United States)
Viola Rieke, Stanford Univ. (United States)
Bruce Daniel, Stanford Univ. (United States)
Graham Sommer, Stanford Univ. (United States)


Published in SPIE Proceedings Vol. 4954:
Thermal Treatment of Tissue: Energy Delivery and Assessment II
Thomas P. Ryan, Editor(s)

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